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Renal primitive neuroectodermal tumour-Ewing Family Tumour

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Clinical features

  • Rare
  • Young adolescents
  • Aggressive clinical course

Cytopathology (similar to Ewing Family tumours (EFT) elsewhere)


  • Tigroid background
  • Small round blue cells
  • Dark and light cells
  • Isolated cells and rosettes
  • Nuclei with fine chromatin
  • Scarce cytoplasm with small glycogen vacuoles


  • CD99: positive
  • NSE: positive
  • Chromogranin: generally negative
  • Synaptophysin: positive- focal
  • Cytokeratin: focal positivity-( seen in only 10-20% of the tumour)

Genetic studies:

  • t(11;22)(q24;q12)

Differential diagnosis

  • Neuroblastoma
    • Generally in the adrenal gland; can involve the upper pole of the kidney
    • Typically in younger children
    • Fibrillary background
    • CD99: negative
    • Absence of t(11;22)(q24;q12)
  • Nephroblastoma-blastemal type
    • Younger patients
    • Blastemal cells are more aggregated than the PNET cells
    • CD99: can be positive
    • Absence of t(11;22)(q24;q12)
    • WT1:positive
  • Clear cell sarcoma of the kidney
    • Younger patients
    • Nuclei with clear chromatin
    • CD99: negative
    • Absence of t(11;22)(q24;q12)

Main points

Molecular demonstration of t(11;22)(q24;q12) is sometimes essential, to distinguish from Wilms’ tumour